Motec PDM15 0v groups

Hi all,

Does anyone know if the PDM15 has separate 0v groups that are meant to pair with specific 12v inputs? The documentation doesn't mention this, but the CAN wiring specifically calls for pulling 0v from connector A (not sure why, might just be arbitrary). There are two separate 0v (one from connector A, and one from connector B); which made me curious / suspicious.

Thanks in advance.

Hi Robert,

The 0V's are not designed to be paired with any of the Outputs on the PDM, they are designed to work with the Inputs. Ground circuitry for the Switched Outputs is done through the vehicles ground, not the PDM.

The 0v's are used on the other side of a switch to the Input, so that when the switch is turned on, the Input Pin is pulled down to 0v.

The 0v does not need to be connected to the CAN Connector.

Hi Stephen,

I was referring only to the 12v inputs (switches). I realize the outputs would go to the vehicle ground. For instance, if I connect input pin A27 to "ground", there are two 0v options (A28 and B22). I don't see anything in the documentation to suggest that some inputs are meant to be paired with one of the two 0v, but I know this pairing exists on the ECU, so I wanted to be sure.

Per the CAN, I should have been more specific. I was referring to the UTC wiring, which calls for 0v going to one of the XLR pins (see attached). These are taken from the Motec website and the PDM manual.

The 0v pins are internally connected, it doesn't matter which one is used. There are two available to reduce the size of the splice needed compared to a single input.

You can ignore the 0v requirement in that image, the Manual hasn't been updated to remove it.

Perfect. Thank you.